The present invention relates to a fuel cell system and a method for operating the fuel cell system, and more particularly to a technique for discharge processing an anode-off gas when the system is halted due to a problem.
A fuel cell system generates electricity using a combustible fuel gas (hydrogen rich gas), and therefore, when a problem occurs in the system, the supply of fuel gas to the fuel cell must be cut off to ensure the safety of the system. For example, Japanese Patent Application Laid-open No. 61-147465 proposes a technique for protecting a fuel cell according to which, during an emergency stoppage caused by operating trouble in the fuel cell, electromagnetic valves disposed at both the inlet and outlet of both an anode and a cathode of the fuel cell stack are closed, and the differential pressure generated between the two electrodes during the emergency stoppage is suppressed to a minimum by providing a constitution in which the anode and cathode are connected to respective inert gas buffer tanks.